脊髓小胶质细胞参与大鼠功能性慢性内脏痛的维持

SPINAL MICROGLIA ACTIVATION IS INVOLVED IN THE MAINTENANCE OF FUNCTIONAL CHRONIC VISCERAL PAIN IN RATS

目的：探讨脊髓小胶质细胞对大鼠功能性慢性内脏痛维持的影响.方法：新生雄性Sprague-Dawley（SD）大鼠30只,随机分成2组（n=15）：假手术组（S组）,新生期结直肠扩张组（CRD组）.CRD组大鼠出生后第8、10、12天,每天给予两次结直肠扩张.出生后第6、8、12周,检测腹壁撤退反射（AWR）评分、痛阈以及腹外斜肌放电（EMG）幅度.HE染色观察结直肠病理改变,取脊髓L2～S4节段,通过免疫荧光计数脊髓背角活化的小胶质细胞,计算小胶质细胞活化率.结果：第6、8、12周两组大鼠结直肠无明显病理改变;与S组相比,CRD组大鼠在20、40、60、80 mmHg结直肠压力下AWR评分、EMG幅度明显增加,痛阈降低（P＜0.05）;且小胶质细胞活化数及活化率明显增加（P＜0.05）.结论：脊髓小胶质细胞活化参与大鼠功能性慢性内脏痛的维持过程.

Objective： To investigate the effect of spinal microglia on the maintenance of functional chronic visceral pain in rats. Methods： Thirty newborn male Sprague-Dawley（SD） rats were randomly divided into two groups （n = 15）： sham operation group （S group） and neonatal colorectal distension group （CRD group）. CRD group rats were given colorectal distension twice daily on postnatal 8th, 10th, 12th day. Abdominal withdrawal reflex （AWR） scores, pain threshold, and external oblique discharge （electromyography, EMG） amplitude were measured at postnatal 6th, 8th, 12th week. HE staining was used to detect pathological change of the colorectal tissue. Spinal L2-$4 segment were taken out to count activated microglia and calculate microglial activation rate in the spinal dorsal horn by using immunofluorescence. Results： No apparent colorectal pathological change was observed between two groups at 6th, 8th, 12th week. Compared with S group, the AWR scores, EMG amplitude in CRD group rats were significantly higher at 20, 40, 60 and 80 mm Hg distention pressures and pain threshold was decreased （P 〈 0.05）. Furthermore, the number of activated microglia and the activation rate was significantly increased （P 〈 0.05）. Conclusion： Spinal microglial activation is involved in maintenance of functional chronic visceral pain in rats.